This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application for A STEREOSCOPIC VIDEO DISPLAY SYSTEM USING A POLARIZATION CHARACTERISTIC OF LIQUID CRYSTAL TYPE DISPLAY PANEL earlier filed in the Korean Industrial Property Office on Jul. 4, 2000 and there duly assigned Serial No. 2000-38039.
The present invention relates to a stereoscopic image display system using polarization characteristics of a liquid crystal device panel and an illumination device for the liquid crystal device panel, and more particularly to a stereoscopic image display system using polarization characteristics of a liquid crystal device panel and an illumination unit for the liquid crystal device panel, capable of forming viewing zones for different images on the right and left by transmitting image signals with the same polarization characteristics as the polarization surfaces, wherein the liquid crystal device panel is disposed at an entrance pupil or an exit pupil of projection optics and has a polarization plate formed with two polarization surfaces of different polarization characteristics joined at a center line.
According to the present invention, inconvenience can be removed that is caused by using auxiliary tools such as spectacles or shutter spectacles having the same optical characteristics used in a moving viewing zone mode employing a color difference, a polarization difference, a time difference, and so on used to realize a conventional stereoscopic image as images of the left and right eyes.
Moreover, the present invention can realize a non-spectacles type stereoscopic image system and a multiple viewing-point stereoscopic image system based on a head tracking mode by using the polarization characteristics of a liquid crystal device panel which separates left and right zones.
In general, a stereoscopic image display system is a system that enables a viewer to stereoscopically recognize images by projecting the images viewed in different directions on the left and right eyes in use of a binocular parallax.
In the mean time, for the modes of separating images of the left and right eyes, there are a moving viewing zone mode of a spectacles type which uses a color difference, a polarization difference, a time difference, and so on, and a fixed viewing zone mode of a non-spectacles type which uses specialized optical parts.
In the moving viewing zone mode, a stereoscopic perception is obtained in use of spectacles having the same optical characteristics as the images projected on the left and right eyes or in use of shutter spectacles which open and close in the same period as that alternating and projecting the images projected on the left and right eyes. In this case, the spectacles play a role of the moving viewing zone since a user can move while wearing the spectacles.
In the fixed viewing zone mode, a viewing zone is formed on the whole screen on which images are projected, given as images of a pupil of a projection optics which projects images corresponding to the left and right eyes by a screen. In this case, the movements of a viewing zone are available in part by the viewing point or the head tracking mode, but the range of which is limited.
For a stereoscopic image display system of using polarization characteristics, there are a spectacles type of using polarization spectacles and a non-spectacles type of using a polarization strip plate so far.
The above polarization spectacles type was developed in about 1890, in which the stereoscopic perception is obtained by projecting images corresponding to the left and right eyes on a screen with polarization directions thereof different to each other in 90 degrees, using polarization spectacles which arrange polarization plates having the same polarization directions as images on the eyes, and transmitting only the images having the polarizations of spectacles corresponding to the respective eyes.
A polarization strip plate is a plate in which polarization strips are alternatively arranged in 90 degrees difference to each other in a polarization direction, which are arranged for respective images corresponding to the left and right eyes by pixel lines and then tightly contacted to a liquid crystal device plate, to thereby separate the images corresponding to the left and right eyes by respective polarization. Next, the separated images are convergent through a Fresnel lens to form a viewing zone, to thereby recognize the stereoscopic perception.
However, in case of the polarization spectacles type, there exists a problem in that a user has to wear spectacles first of all and the stereoscopic perception gets lost since images in two polarization directions are mixed up with the head of the user turning a bit to the left or right side. Further, in case of the polarization strip plate, there exists a problem in that the polarization spectacles type is hardly realized since there exist difficulties in establishing a distance between a polarization strip plate and a liquid crystal device panel and a correspondence relation between a polarization strip width and a pixel line width of the liquid crystal device panel.
In order to review in more detail the problems of the conventional stereoscopic image display system, a description on a structure and operations of the most common stereoscopic image display system will be made as follows.
U.S. Pat. No. 5,132,839 issued to Travis for Three Dimensional Display Device discloses a stereoscopic image display unit including an image display unit is constituted with a cathode-ray tube(CRT) for three red(R), green(G), and blue(B) colors and a beam splitter for converging an image displayed on the CRT in one direction. An image displayed on the image display unit is projected on a projection screen through an exit pupil of a projection lens.
Accordingly, an image of the exit pupil of the projection lens is formed on the front side of the screen, which operates as a viewing zone. In order to form a stereoscopic viewing zone, first and second shutters are disposed to bisect the exit pupil.
In operations of the stereoscopic image display system based on the shutters, if an image corresponding to the left eye is displayed on the image display unit, the first shutter opens and the second shutter closes, in order for an image by the screen of the second shutter to work as a left side viewing zone. Further, if an image according to the right eye, the second shutter opens and the first shutter closes, in order for an image by the screen of the first shutter to work as a right side viewing zone.
At this time, by placing the left side viewing zone 6.5 cm (centimeters) away from the right side viewing zone to correspond to the distance of the eyes, a viewer can perceive a stereoscopic image. In order to display a stereoscopic image by the shutters, the image display unit has to have a response speed at least twice as fast compared to a general image display unit.
The first and second shutters transmit only images corresponding to the eyes, so that the brightness of the images on the screen is reduced in a reverse proportion to the number of shutters.
U.S. Pat. No. 5,703,717 issued to Ezra et al. for Three-Dimensional Projection Display Apparatus discloses a stereoscopic image display system including an image display unit constituted with first and second image display plates and for displaying images corresponding to the left and right eyes and first and second light sources for independently illuminating the first and second image display plates respectively through first and second focusing lenses.
Light transmitted through the first and second image display plates become incident on a projection lens by a beam indicator. The light incident on the projection lens is projected to an image screen again, an image of an exit pupil of the projection lens by the image projection screen is formed on the front side of the image projection screen.
At this time, an image by the first light source is formed on the right side of the exit pupil through the first focusing lens, and an image of the second light source is formed on the left side of the exit pupil through the second focusing lens.
That is, the images through the first and second focusing lens of the first and second light sources are focused again by the image projection screen to form the viewing zones.
The above system has a problem in that the use of focusing lenses is required, the positions of the light sources and the focusing lenses should be exact since viewing zones are formed by images of light sources, primary images by the focusing lenses of the light sources should be exactly formed in the exit pupils of the projection lenses, and opaque portions occur in case that a user makes the movements of a viewing point since the left and right viewing zones become intermittent unless the images of the light sources are exactly superimposed and then combined.
Further, the above system causes troublesomeness in that the positions of the light sources move with viewing points in order to display the multiple viewing-point images.
It is therefore an object of the present invention to provide a stereoscopic image display system using polarization characteristics of a liquid crystal device panel, capable of providing a stereoscopic perception of images without wearing spectacles by disposing in an entrance pupil or in an exit pupil of a projection lens a polarization plate arranged for two polarization plates of an original polarization opposite to each other in polarization directions or for two linear polarization plates having a polarization direction of a 90 degree difference to each other to be fitted in the left and right sides on a center line, projecting left and right images of a display device panel on a screen through a projection lens in the left and right polarization directions of the polarization plate, and getting different images from images of the polarization plate or images of a viewing zone incident on the left and right eyes respectively.
It is another object to have a stereoscopic image display system that can be easily manufactured and easily used.
It is still another object to have a stereoscopic image display system that can reduce the cost of manufacture.
It is yet another object to have a stereoscopic image display system that can increase the quality of the image being viewed without fatiguing the eyes of a user.
A structure of the present invention for achieving the above objects includes a phase retarder which polarizes a light source of images coming out of two liquid crystal display panels to have a phase difference of 90 degrees or causes the light source to have circular polarization in a different direction, a polarization beam splitter, a polarization plate, plural lenses, a light source for irradiating light on the liquid crystal display panels, an image projection screen for projecting images by converging light sources having the image information, and so on.
According to the present invention, inconvenience can be removed that is caused by using auxiliary tools such as spectacles or shutter spectacles having the same optical characteristics used in a moving viewing zone mode employing a color difference, a polarization difference, a time difference, and so on used to realize a conventional stereoscopic image as images of the left and right eyes.
Moreover, the present invention can realize a non-spectacles type stereoscopic image system and a multiple viewing-point stereoscopic image system based on a head tracking mode by using the polarization characteristics of a liquid crystal device panel which separates left and right zones.